On Sun, Aug 11, 2024 at 9:30 PM David Rientjes <rientjes@xxxxxxxxxx> wrote:
>
> On Wed, 7 Aug 2024, Pedro Falcato wrote:
>
> > diff --git a/mm/slab_common.c b/mm/slab_common.c
> > index 40b582a014b..1abe6a577d5 100644
> > --- a/mm/slab_common.c
> > +++ b/mm/slab_common.c
> > @@ -88,6 +88,19 @@ unsigned int kmem_cache_size(struct kmem_cache *s)
> > EXPORT_SYMBOL(kmem_cache_size);
> >
> > #ifdef CONFIG_DEBUG_VM
> > +
> > +static bool kmem_cache_is_duplicate_name(const char *name)
> > +{
> > + struct kmem_cache *s;
> > +
> > + list_for_each_entry(s, &slab_caches, list) {
> > + if (!strcmp(s->name, name))
> > + return true;
> > + }
> > +
> > + return false;
> > +}
> > +
> > static int kmem_cache_sanity_check(const char *name, unsigned int size)
> > {
> > if (!name || in_interrupt() || size > KMALLOC_MAX_SIZE) {
> > @@ -95,6 +108,11 @@ static int kmem_cache_sanity_check(const char *name, unsigned int size)
> > return -EINVAL;
> > }
> >
> > + if (kmem_cache_is_duplicate_name(name)) {
> > + /* Duplicate names will confuse slabtop, et al */
> > + pr_warn("%s: name %s already exists as a cache\n", __func__, name);
>
>
> Shouldn't this be a full WARN_ON() instead of pr_warn()? I assume we'll
> be interested in who is adding the cache when the name already exists.
panic_on_warn? :)
Personally I don't have anything against WARN_ON, but we've seen that
panic_on_warn is a real thing on real systems, and DEBUG_VM is also
set on real prod configs (like Fedora does/used to do). I've sent out
one or two loose patches for problems I did find in my own testing
around, but there may be many more (e.g some drivers may call
kmem_cache_create repeatedly in some sort of callback, like 9pfs was
doing when mounting; this is not greppable). And I'd guess grepping
for cache names tends to be easy enough?
--
Pedro
